Hallucinations do not originate in a single region of the brain, the thalamus, and cannot be traced back to a single pathological mechanism. They emerge from the complex interaction of several brain regions, and are not necessarily the result of sensory impairment or the effect of a defective filter. In the case of schizophrenia, hallucinations are accessory symptoms, in Bleuler's sense, and are thus not central to this disorder.

Typically, thalamic aphasias appear to be primarily lexical-semantic disorders representing difficulty using stored declarative memories for semantic information to access lexical word forms. Yet, there also is reason to believe that the thalamus might play a role in linguistic procedural memory. For more than two decades, we have known that basal ganglia dysfunction is associated with difficulties in procedural learning, and specific thalamic nuclei are the final waypoint back to the cortex in cortico-basal ganglia-cortical loops. Recent analyses of the (...) role of the thalamus in lexical-semantic processes and of the role of the basal ganglia in linguistic processes suggest that thalamic participation is not simply a matter of declarative vs. procedural memory, but a matter of how the thalamus participates in lexical-semantic processes and in linguistic procedural memory, as well as the interaction of these processes. One role for the thalamus in accessing lexical forms for semantic concepts relates to the stabilization of a very complex semantic-lexical interface with thousands of representations on both sides of the interface. Further, the possibility is discussed that the thalamus, through its participation in basal ganglia loops, participates in two linguistic procedural memory processes: syntactic/grammatical procedures and procedures for finding words to represent semantic concepts, with the latter interacting intricately with declarative memories. These concepts are discussed in detail along with complexities that can be addressed by future research. (shrink)

There is a paucity of treatment options for cognitively normal individuals with drug resistant genetic generalized epilepsy. Centromedian nucleus of the thalamus deep brain stimulation may be a viable treatment for GGE. Here, we present the case of a 27-year-old cognitively normal woman with drug resistant GGE, with childhood onset. Seizure semiology are absence seizures and generalized onset tonic clonic seizures. At baseline she had 4–8 GTC seizures per month and weekly absence seizures despite three antiseizure medications and vagus (...) nerve stimulation. A multidisciplinary committee recommended off-label use of CM DBS in this patient. Over 12-months of CM DBS she had two GTC seizure days, which were in the setting of medication withdrawal and illness, and no GTC seizures in the last 6 months. There was no significant change in the burden of absence seizures. Presently, just two studies clearly document CM DBS in cognitively normal individuals with GGE or idiopathic generalized epilepsy [in contrast to studies of cognitively impaired individuals with developmental and epileptic encephalopathies ]. Our results suggest that CM DBS can be an effective treatment for cognitively normal individuals with GGE and underscore the need for prospective studies of CM DBS. (shrink)

Aggleton & Brown propose that familiarity-based recognition depends on a perirhinal-medial dorsal thalamic system. However, connections between these structures are sparse or absent. In contrast, the perirhinal cortex is connected to midline/intralaminar nuclei. In a human, a lesion in this thalamic domain, sparing the medial dorsal nucleus, impaired familiarity-based recognition while sparing recollective-based recognition. It is thus more likely that the intralaminar/midline nuclei are involved in recognition.

Three questions arising from Aggleton & Brown's target article are addressed. (1) Is there any benefit to considering the effects of partial lesions of the anterior thalamic nuclei (AT)? (2) Do the AT have a separate role in the proposed extended hippocampal system? (3) Should perirhinal cortex function be restricted to familiarity judgements?

One of the most compelling questions still unanswered in neuroscience is how consciousness arises. In this article, we examine visual processing, the parietal lobe, and contralateral neglect syndrome as a window into consciousness and how the brain functions as the mind and we introduce a mechanism for the processing of visual information and its role in consciousness. We propose that consciousness arises from integration of information from throughout the body and brain by the thalamus and that the thalamus (...) reimages visual and other sensory information from throughout the cortex in a default three-dimensional space in the mind. We further suggest that the thalamus generates a dynamic default three-dimensional space by integrating processed information from corticothalamic feedback loops, creating an infrastructure that may form the basis of our consciousness. Further experimental evidence is needed to examine and support this hypothesis, the role of the thalamus, and to further elucidate the mechanism of consciousness. (shrink)

The Global Workspace Theory and Information Integration Theory are two of the most currently accepted consciousness models; however, these models do not address many aspects of conscious experience. We compare these models to our previously proposed consciousness model in which the thalamus fills-in processed sensory information from corticothalamic feedback loops within a proposed 3D default space, resulting in the recreation of the internal and external worlds within the mind. This 3D default space is composed of all cells of the (...) body, which communicate via gap junctions and electrical potentials to create this unified space. We use 3D llustrations to explain how both visual and non-visual sensory information may be filled-in within this dynamic space, creating a unified seamless conscious experience. This neural sensory memory space is likely generated by baseline neural oscillatory activity from the default mode network, other salient networks, brainstem, and reticular activating system. (shrink)

Objective Manic and depressive phases of bipolar disorder (BD) show opposite psychomotor symptoms. Neuronally, these may depend on altered relationships between sensorimotor network (SMN) and subcortical structures. The study aimed to investigate the functional relationships of SMN with substantia nigra (SN) and raphe nuclei (RN) via subcortical-cortical loops, and their alteration in bipolar mania and depression, as characterized by psychomotor excitation and inhibition. -/- Method In this resting-state functional magnetic resonance imaging (fMRI) study on healthy (n = 67) and BD (...) patients (n = 100), (1) functional connectivity (FC) between thalamus and SMN was calculated and correlated with FC from SN or RN to basal ganglia (BG)/thalamus in healthy; (2) using an a-priori-driven approach, thalamus-SMN FC, SN-BG/thalamus FC, and RN-BG/thalamus FC were compared between healthy and BD, focusing on manic (n = 34) and inhibited depressed (n = 21) patients. -/- Results (1) In healthy, the thalamus-SMN FC showed a quadratic correlation with SN-BG/thalamus FC and a linear negative correlation with RN-BG/thalamus FC. Accordingly, the SN-related FC appears to enable the thalamus-SMN coupling, while the RN-related FC affects it favoring anti-correlation. (2) In BD, mania showed an increase in thalamus-SMN FC toward positive values (ie, thalamus-SMN abnormal coupling) paralleled by reduction of RN-BG/thalamus FC. By contrast, inhibited depression showed a decrease in thalamus-SMN FC toward around-zero values (ie, thalamus-SMN disconnection) paralleled by reduction of SN-BG/thalamus FC (and RN-BG/thalamus FC). The results were replicated in independent HC and BD datasets. -/- Conclusions These findings suggest an abnormal relationship of SMN with neurotransmitters-related areas via subcortical-cortical loops in mania and inhibited depression, finally resulting in psychomotor alterations. (shrink)

If we were to connect two individuals’ brains together, how would this affect the individuals’ conscious experiences? In particular, it is possible for two people to share any of their conscious experiences; to simultaneously enjoy some token experiences while remaining distinct subjects? The case of the Hogan twins—craniopagus conjoined twins whose brains are connected at the thalamus—seems to show that this can happen. I argue that while practical empirical methods cannot tell us directly whether or not the twins share (...) conscious experiences, considerations about the locality of content processing in the brain entails that they most likely do so. (shrink)

The explanatory gap . Consciousness is a mystery. No one has ever given an account, even a highly speculative, hypothetical, and incomplete account of how a physical thing could have phenomenal states. Suppose that consciousness is identical to a property of the brain, say activity in the pyramidal cells of layer 5 of the cortex involving reverberatory circuits from cortical layer 6 to the thalamus and back to layers 4 and 6,as Crick and Koch have suggested for visual consciousness. (...) .) Still, that identity itself calls out for explanation! Proponents of an explanatory gap disagree about whether the gap is permanent. Some say that we are like the scientifically naive person who is told that matter = energy, but does not have the concepts required to make sense of the idea. If we can acquire these concepts, the gap is closable. Others say the gap is uncloseable because of our cognitive limitations. Still others say that the gap is a consequence of the fundamental nature of consciousness. (shrink)

BackgroundResponsive neurostimulation has been utilized as a treatment for intractable epilepsy. The RNS System delivers stimulation in response to detected abnormal activity, via leads covering the seizure foci, in response to detections of predefined epileptiform activity with the goal of decreasing seizure frequency and severity. While thalamic leads are often implanted in combination with cortical strip leads, implantation and stimulation with bilateral thalamic leads alone is less common, and the ability to detect electrographic seizures using RNS System thalamic leads is (...) uncertain.ObjectiveThe present study retrospectively evaluated fourteen patients with RNS System depth leads implanted in the thalamus, with or without concomitant implantation of cortical strip leads, to determine the ability to detect electrographic seizures in the thalamus. Detailed patient presentations and lead trajectories were reviewed alongside electroencephalographic analyses.ResultsAnterior nucleus thalamic leads, whether bilateral or unilateral and combined with a cortical strip lead, successfully detected and terminated epileptiform activity, as demonstrated by Cases 2 and 3. Similarly, bilateral centromedian thalamic leads or a combination of one centromedian thalamic alongside a cortical strip lead also demonstrated the ability to detect electrographic seizures as seen in Cases 6 and 9. Bilateral pulvinar leads likewise produced reliable seizure detection in Patient 14. Detections of electrographic seizures in thalamic nuclei did not appear to be affected by whether the patient was pediatric or adult at the time of RNS System implantation. Sole thalamic leads paralleled the combination of thalamic and cortical strip leads in terms of preventing the propagation of electrographic seizures.ConclusionThalamic nuclei present a promising target for detection and stimulation via the RNS System for seizures with multifocal or generalized onsets. These areas provide a modifiable, reversible therapeutic option for patients who are not candidates for surgical resection or ablation. (shrink)

Contemporary neuroscientific theories of consciousness are typically based on the study of vision and have neglected olfaction. Several of these (e.g. Global Workspace Theories, the Information Integration theory, and the various theories offered by Crick and Koch) claim that a thalamic relay is necessary for consciousness. Studies on olfaction and the olfactory system's anatomical structure show this claim to be incorrect, thus showing these theories to be either false or inadequate as general and comprehensive accounts of consciousness. Attempts to rescue (...) these theories by claiming that there is a structure in the olfactory system that is functionally equivalent to the thalamus in the visual system, such as the olfactory bulb or the olfactory cortex, are also shown to fail. If we wish to understand consciousness, we have to wake up and smell it. (shrink)

I propose that primary conscious awareness arises from synchronized activity in dendrites of neurons in dorsal thalamic nuclei, mediated particularly by inhibitory interactions with thalamic reticular neurons. In support, I offer four evidential pillars: consciousness is restricted to the results of cortical computations; thalamus is the common locus of action of brain injury in vegetative state and of general anesthetics; the anatomy and physiology of the thalamus imply a central role in consciousness; neural synchronization is a neural correlate (...) of consciousness. (shrink)

The fetal human possesses an active central nervous system from at least the eighth week of development. Until mid-gestation the most significant center of activity is the brainstem. By the end of the first trimester, it appears that the brainstem could be acting as a rudimentary modulator of sensory information and motor activity. What importance ought to be attached to such regulatory activity is uncertain. Some argue that it represents a level of integrated activity sufficient to bolster an argument for (...) conferring some measure of standing at this point. Our thinking about sentience is not advanced a great deal, as we as yet have no good way of talking about it at the brainstem level. As for the neocortex, available evidence indicates that it does not become a functional part of the neuraxis until at least mid-gestation. It is not until then that the thalamus – the major gateway for sensory input to the cerebrum – makes its first afferent contacts with the neocortex. Keywords: neuromaturation, fetal behavior, fetal brainstem CiteULike Connotea Del.icio.us What's this? (shrink)

The study of consciousness is poised today at interesting crossroads. There has been a surge of research into various neurobiological underpinnings of consciousness in the past decade. The present article looks at the theories regarding this complex phenomenon, especially the ones that neurobiology, cognitive neuroscience and cognitive psychology have to offer. We will first discuss the origin and etymology of word consciousness and its usage. Neurobiological correlates of consciousness are discussed with structures like the ascending reticular activating system, the amygdala, (...) the cerebellum, the thalamus, the frontoparietal circuits, the prefrontal cortex and the precuneus. The cellular and microlevel theories of consciousness and cerebral activity at the neuronal level contributing to consciousness are highlighted, along with the various theories posited in this area. The role of neuronal assemblies and circuits along with firing patterns and their ramifications for the understanding of consciousness are discussed. A section on the role of anaesthesia and its links to consciousness is presented, along with details of split-brain studies in consciousness and altered states of awareness, including the vegetative states. The article finally discusses the progress cognitive psychology has made in identifying and theorising various perspectives of consciousness, perceptual awareness and conscious processing. Both recent and past researches are highlighted. The importance and salient features of each theory are discussed along with the pitfalls, if present. A need for integration of various theories to understand consciousness from a holistic perspective is stressed, to enable one to reach a theory that explains the ultimate neurobiology of consciousness. (shrink)

BackgroundFear of abandonment and aloneness play a key role in the clinical understanding interpersonal and attachment-specific problems in patients with borderline personality disorder and has been investigated in previous functional Magnet Resonance Imaging studies. The aim of the present study was to examine how different aspects of attachment representations are processed in BPD, by using for the first time an fMRI attachment paradigm including personalized core sentences from the participants’ own attachment stories. We hypothesized that BPD patients would show increased (...) functional involvement of limbic brain regions associated with fear and pain when presented personalized attachment relevant stimuli representing loneliness compared to healthy controls.MethodsWe examined the attachment classifications of 26 female BPD patients and 26 female HC using the Adult Attachment Projective Picture System. We used an fMRI-adapted attachment paradigm to investigate the neural correlates of attachment. All participants were presented three personalized sentences extracted from their AAP attachment narrative, combined with standardized AAP pictures representing being alone or in interactive attachment situations.ResultsAs expected, the classification of unresolved attachment was significantly greater in BPD compared to HC. BPD patients showed increased fMRI-activation in brain areas associated with fear, pain, and hyperarousal than HC when presented with personalized attachment-relevant alone stimuli. In particular, pictures with monadic attachment situations induced greater anterior medial cingulate cortex, anterior insula, amygdala, thalamus and superior temporal gyrus activation in the patient group.ConclusionThe results point to increased fMRI-activation in areas processing emotional distress and painful experiences in BPD patients. In particular, the emotional cascade reflecting attachment distress was evoked by combining monadic pictures, representing abandonment and aloneness, with the patients’ personalized narrative material. Our results confirmed and replicated previous results that illustrate once again the high relevance of aloneness and feelings of abandonment for BPD in the context of attachment trauma. Moreover, our results support the hypothesis of hypermentalization in response to attachment distress as a core feature of social-cognitive impairment in BPD associated with common treatment implications across different therapeutic orientations. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Life in LimboM. ChiuWhen my son was 7 years old, he began complaining of headaches. They were frequent, but never seemed severe. “I have a headache!” was always followed by “Can I watch TV?” I didn’t believe the pain was real until it woke him up in the middle of the night. I knew then that something must be wrong. I approached our pediatrician, who said it sounded like (...) migraines, but we should order an MRI to rule anything out. The appointment was scheduled several months in advance, and I always had the urge to cancel it. I was pretty sure my son just wanted to watch TV. The pediatrician told me I might as well do the MRI. He told me that if we skipped it and something was wrong, I would never be able to live with the regret. We kept the Monday morning appointment, and went to the MRI expecting reassurance that nothing was wrong. Instead, we got a phone call later that day. They needed to see us on immediately, but wouldn’t tell me why. Of course, I knew something was wrong. “Is it a tumor?” I asked. “This isn’t something we can discuss on the phone” was the answer I got. An appointment was scheduled for Wednesday. Two days might be “immediately” to medical professionals, but to a parent who just heard that her child had an abnormal MRI, it was an eternity. I planned my son’s funeral in those two days.Our meeting with the Neurologist began with reviewing the MRI. “See this spot here? It shouldn’t be there”. A tumor. 1 ½ × 1 ½ × 2 ½ cm tumor, in the right thalamus. Small, they said. Looks like a Low Grade Glioma they said. The kind of tumor you want to have, if you have to have a brain tumor. A biopsy was scheduled for two weeks later. The [End Page E2] biopsy confirmed it was a Juvenile Pilocytic Astrocytoma (JPA). The neurosurgeon was confident she could remove all of the tumor. We were at one of the best Children’s Hospitals in the world. We were in good hands.A few days before the surgery, a friend who is a medical doctor suggested we get a second opinion. “It couldn’t hurt, it could help”, my husband said. Fortunately, he just sold a start–up company, and was planning to take a few months off from work before starting his next venture. He had time to research, talk to friends in the medical field and make phone calls.Our second opinion from another leading hospital reviewed the MRI’s with us. The neurosurgeon asked, “Did they say tumor? One?” Yes, they did. “See this here?” he said, pointing to a second spot on the MRI. He said it was possibly a second tumor, or more likely, an extension of the first. It was in inoperable location. Surgery wasn’t an option. Chemo would be our best choice. Why would we cut into our son’s brain to remove part of the tumor when he would need to do chemo anyway? Why not try chemo first?I would like to say that we do not fault our original neuro–oncology team for missing this second abnormality. It is hard to notice an ant in the room when there is an elephant staring at you. People make mistakes, and tumors don’t always look the same. That’s what second opinions are for. That is why doctors should encourage patients to get second opinions.We scheduled the surgery for port implantation, and got busy educating ourselves about chemo regimes. It was going to be a long journey. 18 months of transfusions with a pretty low success rate and a high rate of secondary complications. Unsure if we were doing the right thing, we got a third opinion. I am so grateful that my husband was between jobs and had time to devote to finding the best possible treatment for our son. We were financially stable and had great insurance. What do people do when they don’t have this luxury?By now, several months had passed since our first MRI. Our... (shrink)

The impact of stroke on motor functioning is analyzed at different levels. ‘Impairment’ denotes the loss of basic characteristics of voluntary movement. ‘Activity limitation’ denotes the loss of normal capacity for independent execution of daily activities. Recovery from impairment is accomplished by ‘restitution’ and recovery from activity limitation is accomplished by the combined effect of ‘restitution’ and ‘compensation.’ We aimed to unravel the long-term effects of variation in lesion topography on motor impairment of the hemiparetic lower limb (HLL), and gait (...) capacity as a measure of related activity limitation. Gait was assessed by the 3 m walk test (3MWT) in 67 first-event chronic stroke patients, at their homes. Enduring impairment of the HLL was assessed by the Fugl–Meyer Lower Extremity (FMA-LE) test. The impact of variation in lesion topography on HLL impairment and on walking was analyzed separately for left and right hemispheric damage (LHD, RHD) by voxel-based lesion-symptom mapping (VLSM). In the LHD group, HLL impairment tended to be affected by damage to the posterior limb of the internal capsule (PLIC). Walking capacity tended to be affected by a larger array of structures: PLIC and corona radiata, external capsule and caudate nucleus. In the RHD group, both HLL impairment and walking capacity were sensitive to damage in a much larger number of brain voxels. HLL impairment was affected by damage to the corona radiata, superior longitudinal fasciculus and insula. Walking was affected by damage to the same areas, plus the internal and external capsules, putamen, thalamus and parts of the perisylvian cortex. In both groups, voxel clusters have been found where damage affected FMA-LE and also 3MWT, along with voxels where damage affected only one of the measures (mainly 3MWT). In stroke, enduring ‘activity limitation’ is affected by damage to a much larger array of brain structures and voxels within specific structures, compared to enduring ‘impairment.’ Differences between the effects of left and right hemisphere damage are likely to reflect variation in motor-network organization and post-stroke re-organization related to hemispheric dominance. Further studies with larger sample size are required for the validation of these results. (shrink)

COMMENTARY ON: LaBerge, D.. Attention, awareness, and the triangular circuit. Consciousness and Cognition, 6, 149-181. ABSTRACT: LaBerge proposes that underlying attention and self-awareness is a triangular circuit involving interconnected posterior cortical, thalamic and prefrontal neural ensembles. While the target paper makes only passing reference to it, the reticular nucleus of the thalamus is an integral part of the triangular circuit he posits. Indeed, it is essential to a complete understanding of his model.

Focal brain metabolic effects detected by proton magnetic resonance spectroscopy (MRS) in obsessive-compulsive disorder (OCD) represent prospective indices of clinical status and guides to treatment design. Sampling bilateral pregenual anterior cingulate cortex (pACC), anterior middle cingulate cortex (aMCC), and thalamus in 40 adult patients and 16 healthy controls, we examined relationships of the neurometabolites glutamate+glutamine (Glx), creatine+phosphocreatine (Cr), and choline-compounds (Cho) with OCD diagnosis and multiple symptom types. The latter included OC core symptoms (Yale-Brown Obsessive-Compulsive Scale - YBOCS), depressive (...) symptoms (Montgomery-Åsberg Depression Rating Scale - MADRS), and general functioning (Global Assessment Scale - GAS). pACC Glx was 9.7% higher in patients than controls. Within patients, Cr and Cho correlated negatively with YBOCS and MADRS, while Cr correlated positively with the GAS. In aMCC, Cr and Cho correlated negatively with MADRS, while Cr in thalamus correlated positively with GAS. These findings present moderate support for glutamatergic and cingulocentric perspectives on OCD. Based on our prior metabolic model of OCD, we offer one possible interpretation of these group and correlational effects as consequences of a corticothalamic state of elevated glutamatergic receptor activity alongside below-normal glutamatergic transporter activity. (shrink)

If successive, brief visual images are exposed for recognition or for psychophysical ratings, various effects and phenomena of fast dynamics of conscious perception such as mutual masking, metacontrast, proactive enhancement of contrast, proactive speed-up of the latency of subjective visual experience, the Fröhlich Effect, the Tandem Effect, attentional facilitation by visuospatial precuing, and some others have been found. The theory proposed to deal with these phenomena proceeds from the assumption that two types of brain processes are necessary in order to (...) consciously recognize visual stimuli: fast, specific processes of encoding that allocate and reactivate the stimulus representation which is based on the activity of selected cortical neurons and relatively slower processes of facilitation of the activity of this specific representation that are mediated by the excitatory modulation of the EPSPs of those selected cortical neurons by the ascending input from nonspecific thalamus. Theperceptual retouchconstruct is proposed in order to characterize and analyze the interaction of and . The neurophysiological characteristics of this bifunctional system of afference help to put forward several predictions that are found to be consistent with the empirical regularities of the above-described perceptual-attentional phenomena. These data form a body of converging evidence that is consistent with the predictions of the perceptual retouch approach. (shrink)

Explaining the nature and mechanisms of conscious experience in neurobiological terms seems to be an attainable, if yet unattained, goal. Research at many levels is important, including research at the cellular level that explores the role of recurrent pathways between thalamic nuclei and the cortex, and research that explores consciousness from the perspective of action. Conceptually, a clearer understanding of the logic of expressions such as ‘‘causes’’ and ‘‘correlates’’, and about what to expect from a theory of consciousness are required. (...) The logic of some terms, such as ‘‘qualia’’ and ‘‘reductionism’’, continues to generate misunderstandings about the scientific possibilities and limits. Experimentally, a deeper understanding of the role of the thalamus in coordinating activity across cortical levels, and a readiness to reconsider the orthodox approach to thalamocortical organization are also required. (shrink)

I have argued in other work that emotion, attentional functions, and executive functions are three interpenetrant global state variables, essentially differential slices of the consciousness pie. This paper will outline the columnar architecture and connectivities of the PAG (periaqueductal gray), its role in organizing prototype states of emotion, and the re-entry of PAG with the extended reticular thalamic activating system (“ERTAS”). At the end we will outline some potential implications of these connectivities for possible functional correlates of PAG networks that (...) are just starting to be mapped. Overall, we will look at many lines of evidence that PAG should be conceptualized as a peri-reticular structure that has a foundational role in emotion, in generating the meaningful organization of behavior by the brain through prototype emotional states, and in allowing the various emotional systems to globally influence and tune both the forebrain and brainstem. Finally, we address implications of these concepts for what is currently understood about consciousness, underlining the need for somewhat more humility within consciousness studies about our current level of understanding of consciousness in the brain, combined with a deeper appreciation of the intrinsic connections between emotion and consciousness. One hopes that more concerted empirical interest in structures underneath the thalamus, combined with a deeper appreciation for the fundamental role that organismic and social value must have in bootstrapping awareness in the developing brain, would begin more widely to influence the fundamental lines of neuroscientific research in both emotion studies and consciousness studies. (shrink)

This article summarizes a variety of current as well as previous research in support of a new theory of consciousness. Evidence has been steadily accumulating that information about a stimulus complex is distributed to many neuronal populations dispersed throughout the brain and is represented by the departure from randomness of the temporal pattern of neural discharges within these large ensembles. Zero phase lag synchronization occurs between discharges of neurons in different brain regions and is enhanced by presentation of stimuli. This (...) evidence further suggests that spatiotemporal patterns of coherence, which have been identified by spatial principal component analysis, may encode a multidimensional representation of a present or past event. How such distributed information is integrated into a holistic percept constitutes the binding problem. How a percept defined by a spatial distribution of nonrandomness can be subjectively experienced constitutes the problem of consciousness. Explanations based on a discrete connectionistic network cannot be reconciled with the relevant facts. Evidence is presented herein of invariant features of brain electrical activity found to change reversibly with loss and return of consciousness in a study of 176 patients anesthetized during surgical procedures. A review of relevant research areas, as well as the anesthesia data, leads to a postulation that consciousness is a property of quantumlike processes, within a brain field resonating within a core of structures, which may be the neural substrate of consciousness. This core includes regions of the prefrontal cortex, the frontal cortex, the pre- and paracentral cortex, thalamus, limbic system, and basal ganglia. (shrink)

The study of consciousness is poised today at interesting crossroads. There has been a surge of research into various neurobiological underpinnings of consciousness in the past decade. The present article looks at the theories regarding this complex phenomenon, especially the ones that neurobiology, cognitive neuroscience and cognitive psychology have to offer. We will first discuss the origin and etymology of word consciousness and its usage. Neurobiological correlates of consciousness are discussed with structures like the ascending reticular activating system, the amygdala, (...) the cerebellum, the thalamus, the frontoparietal circuits, the prefrontal cortex and the precuneus. The cellular and microlevel theories of consciousness and cerebral activity at the neuronal level contributing to consciousness are highlighted, along with the various theories posited in this area. The role of neuronal assemblies and circuits along with firing patterns and their ramifications for the understanding of consciousness are discussed. A section on the role of anaesthesia and its links to consciousness is presented, along with details of split-brain studies in consciousness and altered states of awareness, including the vegetative states. The article finally discusses the progress cognitive psychology has made in identifying and theorising various perspectives of consciousness, perceptual awareness and conscious processing. Both recent and past researches are highlighted. The importance and salient features of each theory are discussed along with the pitfalls, if present. A need for integration of various theories to understand consciousness from a holistic perspective is stressed, to enable one to reach a theory that explains the ultimate neurobiology of consciousness. (shrink)

In this article we will draw on experiences from our own research on deep brain stimulation of the central thalamus in the minimally conscious state. We describe ethical challenges faced in clinical research involving medical devices and offer several cautionary notes about its funding and the interplay of market forces and scientific inquiry and suggest some reforms.

The idea that the thalamo-cortical system is the crucial constituent of the neurobiological mechanisms of consciousness has a long history. For the last few decades, however, consciousness research has to a large extent overlooked the interplay between the cortex and thalamus. Here we revive an integrated view of the neurobiology of consciousness by presenting and discussing several recent major findings about the role of the thalamocortical interactions in consciousness. Based on these findings we propose a specific cellular mechanism how (...) thalamic nuclei modulate the integration of different processing streams within single cortical pyramidal neurons. This theory is inspired by recent work done in rodents, but it integrates decades of work conducted on various species. We illustrate how this new view readily explains various properties and experimental phenomena associated with conscious experience. We discuss the implications of this idea and some of the experiments that need to be done in order to test it. Our view bridges two long-standing perspectives on the neural mechanisms of consciousness and proposes that cortical and thalamo-cortical processing interact at the level of single pyramidal cells. (shrink)

Although emotion is closely associated with motivation, and interacts with perception, cognition, and action, many conceptualizations still treat emotion as separate from these domains. Here, a comparative/evolutionary anatomy framework is presented to motivate the idea that long-range, distributed circuits involving the midbrain, thalamus, and forebrain are central to emotional processing. It is proposed that emotion can be understood in terms of large-scale network interactions spanning the neuroaxis that form “functionally integrated systems.” At the broadest level, the argument is made (...) that we need to move beyond a Newtonian view of causation to one involving complex systems where bidirectional influences and nonlinearities abound. Therefore, understanding interactions between subsystems and signal integration becomes central to unraveling the organization of the emotional brain. (shrink)

Behind the third ventricle of the human brain a miniscule pedunculate bud, close to the optic thalamus, that is, to the two beds of optic nerves, a gland soft in substance yet containing gritty particles. Function: unknown. Because of its pine-cone shape it is called the conarium or pineal body, even though the recent photographs of it by Nilsson and Lindberg show it to be morphologically reminiscent of nothing so much as the plucked tail of a gamebird, which Simon (...) Dedalus refers to as ‘the pope's nose’. Today it is presumed to be an endocrine gland of some sort, even though there is no doubt that morphogenetically in all vertebrates it is a vestigial unpaired eye. As fossil evidence indicates—and we still find it almost fully developed in some extant amphibians—ancestral vertebrates possessed in addition to the paired bilateral eyes a solitary dorsal eye opening at the top of the skull to the sky. This singular evagination of the brain—something betwixt a visual organ and a gland—seems to hold a special fascination for philosophers. Here we shall consider two of them: René Descartes (1596–1650), the father, as we say, of modern philosophy; and Georges Bataille (1897–1962), the father, as many say, of post-modern philosophy. Three hundred years separate them. Devotion to the pineal body conjoins them. (shrink)

Objective: The dopamine hypothesis is one of the most influential theories of the neurobiological background of schizophrenia (SCZ). However, direct evidence for abnormal dopamine-related subcortical-cortical circuitry disconnectivity is still lacking. The aim of this study was therefore to test dopamine-related substantia nigra (SN)-based striato-thalamo-cortical resting-state functional connectivity (FC) in SCZ. Method: Based on our a priori hypothesis, we analyzed a large sample resting-state functional magnetic resonance imaging (fMRI) dataset from first-episode drug-naïve SCZ patients (n = 112) and healthy controls (n (...) = 82) using the SN as the seed region for an investigation of striato-thalamo-cortical FC. This was done in the standard band of slow frequency oscillations and then in its subfrequency bands (Slow4 and Slow5). Results: The analysis showed in SCZ: (1) reciprocal functional hypo-connectivity between SN and striatum, with differential patterns for Slow5 and Slow4; (2) functional hypo-connectivity between striatum and thalamus, as well as functional hyper-connectivity between thalamus and sensorimotor cortical areas, specifically in Slow4; (3) correlation of thalamo-sensorimotor functional hyper-connectivity with psychopathological symptoms. Conclusions: We demonstrate abnormal dopamine-related SN-based striato-thalamo-cortical FC in slow frequency oscillations in first-episode drug-naive SCZ. This suggests that altered dopaminergic function in the SN leads to abnormal neuronal synchronization (as indexed by FC) within subcortical-cortical circuitry, complementing the dopamine hypothesis in SCZ on the regional level of resting-state activity. (shrink)

We have studied a number of long-term meditators in previous studies. The purpose of this study was to determine if there are differences in baseline brain function of experienced meditators compared to non-meditators. All subjects were recruited as part of an ongoing study of different meditation practices. We evaluated 12 advanced meditators and 14 non-meditators with cerebral blood flow SPECT imaging at rest. Images were analyzed with both region of interest and statistical parametric mapping. The CBF of long-term meditators was (...) significantly higher compared to non-meditators in the prefrontal cortex, parietal cortex, thalamus, putamen, caudate, and midbrain. There was also a significant difference in the thalamic laterality with long-term meditators having greater asymmetry. The observed changes associated with long-term meditation appear in structures that underlie the attention network and also those that relate to emotion and autonomic function. (shrink)

The origin of the isocortex may be seen as a series of gradual changes (each one with an adaptive value) from a reptilian-like cerebral cortex, as proposed by Aboitiz et al., or as a new dorsal pallium derivative in mammals which undergoes a surface expansion concomitant with the expansion of the dorsal tier of the dorsal thalamus.

Subjective consciousness suggests a unity of sensing and perceiving self that is difficult to reconcile with the multiplicity of sensory analyzers and the absence of a convergence zone in the brain. This has led—on the one hand—to the dead-end assumption of a unifying sentient homunculus and—on the other—to a denial of conscious unity. The sketchpad model presented here avoids this dilemma by viewing conscious thought as a selfreferent loop of neural activity, rather than as the information content of a fictitious (...) set of output neurons. Use is made of the numerous neural pathways that originate at various cortical and subcortical areas and terminate in the thalamus. The model assumes that primary sensory outputs are modified by such feedback in the thalamic relay nuclei through hill-climbing processes that tend to optimize global responses. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Roadmap Needed:How to Help Parents Navigate the Worst Day of Their LivesCheryl KilpatrickOn January 14, 2010, our 3–year–old daughter, Maggie, was rushed to an emergency room at a satellite medical center. I am an occupational therapist and was actually scheduled to work at a hospital that day. I was wearing my purple scrubs. Maggie had been showing “strange” symptoms all week that I thought might be a sign that (...) she was getting a cold or the flu. She had been extremely tired, having morning headaches and ataxia (balance problems). When I dropped Maggie off at preschool the morning of January 14, 2010 she began to have trouble using her left arm. The teacher noticed that her smile was crooked. I did a quick neurological assessment and saw that her [End Page E9] left arm was much weaker than her right arm. I thought to myself, “My kid looks as if she is having a stroke. But she is only 3–years–old. This doesn’t make any sense.” The teacher gave me a look as if to say, “Are you going to take Maggie to the hospital or am I going to have to do it?” I just stood there. I suppose I was in the first stages of shock. I turned to the teacher and said, “We are going to the hospital.”As we walked toward the ER admissions desk I was surprised to see that we were the only people in the waiting area. It didn’t take long before we were called into the examination room. The ER doctor did a neurological assessment on Maggie like I had done only 30 minutes earlier and said that a CAT scan was needed. He thought that we would most likely be transferred to a local children’s hospital. The CAT scan revealed that Maggie had a large mass in her thalamus. I just looked at the ER doctor and said, “Just tell me what I need to do and I will do it.” No tears, no screams, no emotion. I just went into “mommy mode” and made sure that my child felt safe every step of the way. My husband was on his way home from a business trip when I called to tell him the news. He had no idea what he would find when he finally got to us.As expected, we were transported by ambulance to the local children’s hospital. I remember sitting in the front seat with the driver and feeling like this was all a dream. It was all very surreal. Maggie calmly chatted with the EMS personnel in the back of the ambulance as if nothing was happening. I had no idea how our lives would change once we reached the hospital. This ride to the hospital began our journey into uncharted territory. Nothing in my life had prepared me for what was about to happen.We arrived at the children’s hospital around 11:00 a.m. As we walked into ER department, I could feel the eyes of the ER staff following us. I turned to look at them and they smiled. The look on their faces told me that something was very wrong with my daughter. I felt like we were a sideshow at the carnival. I hated those looks. I didn’t want their smiles. I wanted to know what was happening. I wanted information.My husband arrived about an hour after our arrival. He walked into the room and found his little girl looking very spacey and unable to walk to him without falling. When Maggie and I stepped out into the hallway to find the restroom, I turned to look back into the room and saw my husband with his face in his hands. He was crying. I was not. I was still in “mommy mode” or just plain shock. I knew that my daughter was not well. But then again, neither was I. I was not crying. I was not screaming. I was numb. What I needed was someone to take my “emotional pulse.”We waited patiently in that small room watching the hours pass by as each doctor came... (shrink)

Fornix problem: Why do lesions of the fornix, which connects the hippocampus (HF) to the medial mammillary nucleus (MMN), often cause no deficits in tasks severely affected by lesions of HF or MMN? Solution: The direct HF feedback to antero ventral (AV) thalamus (MMN [Rightarrow A: implies] AV [Leftrightarrow A: l&r dbl arrow] HF), which is blocked by MMN lesions but not fornix lesions, is sufficient for nonscene-relevant consolidation.

Deep brain stimulation is part of state-of-the-art treatment for medically refractory Parkinson’s disease, essential tremor or primary dystonia. However, there are multiple movement disorders that present after a static brain lesion and that are frequently refractory to medical treatment. Using Holmes tremor as an example, we discuss the effectiveness of currently available treatments and, performing simulations using a Markov Chain approach, propose that DBS with iterative parameter optimization is expected to be more effective than an approach based on sequential trials (...) of pharmacological agents. Since, in DBS studies for HT, the thalamus is a frequently chosen target, using data from previous studies of lesion connectivity mapping in HT, we compared the connectivity of thalamic and non-thalamic targets with a proxy of the HT network, and found a significantly higher connectivity of thalamic DBS targets in HT. The understanding of brain networks provided by analysis of functional connectivity may thus provide an informed framework for proper surgical targeting of individual patients. Based on these findings, we argue that there is an ethical imperative to at least consider surgical options in patients with uncommon movement disorders, while simultaneously providing consistent information regarding the expected effectiveness and risks, even in a scenario of surgical-risk aversion. An approach based on n-of-1 DBS trials may ultimately significantly improve outcomes while informing on optimal therapeutic targets and parameter settings for HT and other disabling and rare movement disorders. (shrink)